With rapid development of communication technologies across the globe, security and reliability of submarine transmission devices are very important to relevant vendors of different countries such as communication equipment manufacturers and equipment suppliers. Once such equipment fails, not only the normal communication will be affected, but also the maintenance cost will be very high. By taking the Internet communication for example, the Internet that links the world is transmitting huge amounts of communication information at every second. Such communication information is conveyed by onshore devices and submarine devices. Onshore devices pack and transmit the communication information, and submarine devices process, send, and receive communication signals including such information. Submarine devices mainly include Submarine Optical Fiber Cable (SOFC), submarine repeater (RPT), and submarine optical Branching Unit (BU). For example, the BU is an optical signal branching unit that combines parts of optical signals or lightwaves of a main optical path or splits the optical signals or lightwaves of the main optical path into branches. When the SOFC on the main optical path needs to be cut off due to a fault or maintenance, other BU parts can ensure that the branches are powered normally, so as to minimize the impact caused by a fault on the transmission signals of the SOFC. Therefore, when a submarine cable system introduces the BU, the function of mutual communication between multiple sites can be implemented, and the usage number of SOFCs can be reduced. The BU is of high practical value.
In the process of developing the present invention, the inventor finds the prior art has at least the following defects: Once a submarine device fails, the normal communication of the Internet is surely affected. Therefore, it becomes very important to locate a fault quickly and determine fault causes. For the fault of the submarine device, mostly a fault is caused by water penetration in such devices or burnout of lines. Such a fault may lead to the failure of the device function, make a certain optical fiber lose the capability of transmitting signals, and definitely bring incontinence to the normal communication. How to effectively detect a fault of a submarine device is a problem that persons skilled in the art expect to solve for a long time.